[Info-vax] [OT] Unix terminal drivers, was: Re: Moving away from OpenVMS

[John Reagan]

"Simon Clubley"  wrote in message news:jp5gd4$khd$1 at dont-email.me...

>Unix terminal drivers have a built in timeout capability (at least the
>ones I am familiar with); the timeout is in units of 0.1 seconds.


Yep, Google "tcsetattr" and you'll find:

In noncanonical mode input is available immediately (without the user having 
to type a line-delimiter character), and line editing is disabled. The 
settings of MIN (c_cc[VMIN]) and TIME (c_cc[VTIME]) determine the 
circumstances in which a read(2) completes; there are four distinct cases:

* MIN == 0; TIME == 0: If data is available, read(2) returns immediately, 
with the lesser of the number of bytes available, or the number of bytes 
requested. If no data is available, read(2) returns 0.

* MIN > 0; TIME == 0: read(2) blocks until the lesser of MIN bytes or the 
number of bytes requested are available, and returns the lesser of these two 
values.

* MIN == 0; TIME > 0: TIME specifies the limit for a timer in tenths of a 
second. The timer is started when read(2) is called. read(2) returns either 
when at least one byte of data is available, or when the timer expires. If 
the timer expires without any input becoming available, read(2) returns 0.

* MIN > 0; TIME > 0: TIME specifies the limit for a timer in tenths of a 
second. Once an initial byte of input becomes available, the timer is 
restarted after each further byte is received. read(2) returns either when 
the lesser of the number of bytes requested or MIN byte have been read, or 
when the inter-byte timeout expires. Because the timer is only started after 
the initial byte becomes available, at least one byte will be read.